Update concepts.md

Author: jpeng-ms

articles/communication-services/concepts/chat/concepts.md

@@ -56,8 +56,10 @@ For customers that use Virtual appointments, refer to our Teams Interoperability
 - For chat threads with more than 20 participants, read receipts and typing indicator features aren't supported.
 - For Teams Interop scenarios, it's the number of Azure Communication Services users, not Teams users, that must be below 20 for the typing indicator feature to be supported.
 - When creating a chat thread, you can set the retention policy between 30 and 90 days.
-- For Teams Interop scenarios, the typing indicator event might contain a blank display name when sent from Teams user.
-- For Teams Interop scenarios, read receipts aren't supported for Teams users.
+- Moreover, in Teams Interop scenarios, there are the following limitations:
+    - The typing indicator event might contain a blank display name when sent from Teams user.
+    - Read receipt feature isn't supported.
+    - Certain identities are not supported (i.e. Bot users, Skype users, etc.)
 
 ## Chat architecture